1. Field of the Disclosure
The present disclosure relates to a magnetic contactor that prevents an overcurrent from flowing in a coil by using a b-contact switch.
2. Background of the Disclosure
Generally, a magnetic contactor is a device that switches power (a current) flowing in a main circuit by using the electromagnet principle.
In the magnetic contactor, a closing operation is normally performed in only a case where when the magnetic contactor is closed, namely, when a movable contact of main power is moved to and contacts a fixed contact, a transient current flows in a coil, and then, when a closed state is maintained, namely, when a contacted state of the contact is maintained, a normal current flows in the coil. Therefore, the coil is not damaged by the rising of a temperature when the insertion is maintained.
As described above, in order to solve a problem such as a coil being damaged, a b-contact switch included in a product limits a current applied to the coil so that an overcurrent does not flow in the coil in a closing operation of the magnetic contactor.
FIG. 1A is a circuit diagram of an electronic circuit part applied to a magnetic contactor. In the electronic circuit part of the magnetic contactor, a plurality of electronic elements for controlling a current flowing a coil L are mounted on a printed circuit board (PCB).
The electronic circuit part includes a plurality of external power input terminals P1 and P2 which receive external power, a bridge diode B/D which is disposed between the external power input terminals P1 and P2 and the coil L, a b-contact switch SW which is disposed between the external power input terminals P1 and P2 and the bridge diode B/D, and a capacitor C that is connected to both ends of the b-contact switch SW.
In this case, the coil L is provided in a state of being wound around a bobbin that is an internal element of a product. When external power is alternating current (AC) power, the bridge diode B/D converts the AC power into direct current (DC) power.
To describe a flow path of the external power, the magnetic contactor is closed, and when the external power (an external current) is applied through the external power input terminals P1 and P2, the applied external current flows to the coil L through the b-contact switch SW having low impedance to drive the coil L. The b-contact switch SW is switched off simultaneously with the driving of the coil L, and thus, the applied external current flows to the coil L through the capacitor C having high impedance. Therefore, an overcurrent which is applied to the coil L when a closed state of the magnetic contactor is maintained is limited.
FIG. 1B is an exploded assembly view of a b-contact switch and a holder in a lower frame of a prior art magnetic contactor. In FIG. 1B, a holder 20 is movably equipped in an upper frame, and a bobbin is provided in a lower frame 12.
When external power is applied to a coil which is wound around the bobbin, a fixed core is changed to an electromagnet by a magnetic field which is generated around the coil, and thus, a movable core is absorbed into a fixed core by a magnetic force. At this time, the holder 20 coupled to an upper portion of the movable core is lowered, and presses a b-contact switch SW to switch off the b-contact switch SW.
However, in the prior art magnetic contactor, when a size of a product is large, the b-contact switch SW may be disposed at each of left and right sides (sides in a width direction) of the product. However, when a product is miniaturized, a free space in which the b-contact switch SW is provided is sufficient, and for this reason, it is difficult to miniaturize the product. Also, when the b-contact switch SW cannot be disposed at each of left and right sides of a product, it is difficult to implement a normal operation.